This project will analyze the arrangement and relation of repetitious and self-complementary sequences in Hela DNA. In the primary experiments radioactive denatured Hela DNA will be digested with exonuclease VIII or SI endonuclease before and after incubation with an excess of short denatured nonradioactive Hela DNA. In addition, DNA fragments with and without self-complementary sequences will be separated by hydroxyapatite chromatography. Such experiments will first determine the number, spacing, and clustering, if any, of self-complementary sequences. Next, the experiments will determine how many middle repetitious sequences are clustered together in particular regions of the genome, the number of such regions and the average spacing of the repetitious sequences within such regions. Finally, and most importantly, the experiments will determine the positions of self-complementary sequences relative to those of the repetitious sequences. The organization of these sequences in the DNA will be compared to that of similar sequences in mRNA and hnRNA. The results and comparisons will be used to test the current models proposed to explain chromosome organization and its relationship to gene regulation.